1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus for recording and reproducing information having a high density by utilizing a near-field light generating element having a very small opening for generating near-field light as a near-field light head.
2. Description of the Related Art
A near-field light generating element is currently utilized as a near-field light head of an information recording and reproducing apparatus or a probe for carrying out optical observation of a sample or an investigation thereof is started.
An information recording and reproducing apparatus using light evolves in a direction of high capacity formation and small size formation and high density formation of record bits is requested therefor. As a countermeasure thereof, there have been carried out researches using a blue purple color semiconductor laser or SIL (Solid Immersion Lens), however, according to the technologies, owing to a problem of the diffraction limit of light, there can be expected promotion of a record density about several times as much as the current record density. In contrast thereto, there is expected an information recording and reproducing method utilizing near-field light as a technology of dealing with optical information of a very small region exceeding the diffraction limit of light.
According to the technology, there is utilized near-field light generated by an interactive action between a very small region and an optical opening having a size equal to or smaller than the wavelength of light and formed at a near-field light head constituting a near-field light generating element. Thereby, there can be dealt with optical information in a region equal to or smaller than the wavelength of light which is regarded as a limit in a conventional optical system. A method of reproducing optical information is carried out by a method in which by irradiating light to a surface of a record medium, much of near-field light localized at a very small mark is converted into scattered light by an interactive action between near-field light and a very small opening (collection mode), or a method in which near-field light generated by a very small opening is irradiated to a surface of a record medium and scattered light converted by an interactive action between the near-field light and very small irregularities recorded with information of the surface of the record medium or a change in an optical constant such as refractive index, is detected by a light receiving element separately provided (illumination mode). Recording is carried out by irradiating near-field light generated at a very small opening to a surface of a record medium to thereby change a shape of a very small region on media (heat mode recording) or changing the refractive index or the transmittance of the very small region (photon mode recording). By using the near-field light head having the optical very small opening exceeding the diffraction limit of light, there is achieved high density formation of record bits exceeding that of a conventional optical information recording and reproducing apparatus.
In such a situation, generally, a constitution of a recording and reproducing apparatus utilizing near-field light is substantially similar to that of a magnetic disk apparatus and in place of a magnetic head, a near-field light head is used. A near-field light head having an optical very small opening attached to a front end of a suspension arm, is floated up to a constant height by the flying head technology and is made to access to an arbitrary data mark present on the desk. In order to make the near-field light head follow the disk rotating at high speed, there is provided a flexure function for stabilizing an attitude of the head in correspondence with waviness of the disk.
According to the near-field light head having such a constitution, as a method of supplying light to an opening, there is provided means for connecting an optical fiber or an optical waveguide to the near-field light head from above or a horizontal direction or irradiating light flux from a laser provided above the near-field light head directly to the near-field light head.
Further, by using an optical fiber probe or a cantilever type optical probe which is represented by a near-field optical microscope and an opening portion of which is sharpened by fabricating an optical fiber, while maintaining a position relative to media by an interactive action of tunnel current or atomic force produced between a probe in a scanning type probe microscope and a surface of a sample, recording, reproducing and observing of information are realized.
Further, there is proposed use of a planar probe formed with an opening having an inverse pyramid structure on a silicon substrate by anisotropic etching. Light is made incident from above or a horizontal direction and by reflection at inside of the pyramid in a shape of an inverse cone, near-field light is generated from an opening present at an apex thereof. The probe is not provided with a sharpened front end, mentioned above, and therefore, the probe can be used as a near-field light head such as a light head or a probe suitable for high-speed recording and reproducing or high-speed observation. According to such a near-field light head, in fabricating an upper face of a substrate and a lower face of the substrate, there are used two sheets or more of photomasks which are finely aligned at two faces of the substrate and the structure of the near-field light head is fabricated by the photolithography technology. However, it is difficult to align the two faces of the photomasks with ultra high accuracy, further, it is very difficult to control a shape of the very small opening owning to an error in a thickness of the substrate or a lattice defect of the substrate. Hence, there is devised a near-field light head fabricated with a very small opening and an optical waveguide for guiding light to the very small opening only at one face of the substrate. Further, by constituting such a structure, smaller size formation and thin shape formation can be carried out.
However, according to the above-described structure of the near-field light head, the very small opening and the optical waveguide for guiding light to the very small opening are fabricated on the same side of the substrate to face a side of a record medium. According to an information recording and reproducing apparatus utilizing near-field light in which a distance between the record medium and the very small opening needs to be about several tens nanometers, there poses a problem that there is not a space for connecting an optical fiber directly to the optical waveguide above the near-field light head, light cannot be made incident from outside on the near-field light head and it is difficult to supply light for generating near-field light by using the near-field light head to the near-field light head.
Therefore, it is an object of the invention to provide an information recording and reproducing apparatus for supplying light for generating near-field light to a near-field light head, generating a sufficiently large amount of near-field light from a very small opening and realizing reproduction and recording with ultra high resolution, recording and reproduction at high speed and high SN ratio formation in an information recording and reproducing apparatus using the near-field light head in which the very small opening and an optical waveguide for guiding light to the very small opening are fabricated on the same side.
Hence, in order to achieve the above-described object, according to a first aspect of the invention, there is provided an information recording and reproducing apparatus which is an information recording and reproducing apparatus comprising a record medium, a light source, a suspension arm, a flexure fixed to the suspension arm, a near-field light head fixed to the flexure and having a very small opening on a side of the record medium, a light guiding structure for guiding light flux from the light source to the near-field light head, and a light receiving portion, for recording or reproducing information by utilizing near-field light, wherein the very small opening and an optical waveguide for guiding light to the very small opening are disposed on a same side of the near-field light head and the light guiding structure comprises an optical propagating portion fixed to the suspension arm, an optical coupling portion fixed to the near-field light head, and an optical connecting portion for optically connecting the optical propagating portion and the optical coupling portion.
Therefore, there can be provided the information recording and reproducing apparatus capable of supplying the light for generating the near-field light to the near-field light head by supplying the light flux from the light source by the optical propagating portion and the optical connecting portion and the optical coupling portion, generating a sufficiently large amount of the near-field light at a vicinity of the very small opening of the near-field light head and realizing reproduction and recording with ultra high resolution, recording and reproduction at high speed and high SN ratio formation even in the information recording and reproducing apparatus using the near-field light head in which the very small opening and the optical waveguide for guiding light to the very small opening are fabricated on the same side.
Further, according to a second aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical coupling portion comprises a prism and a gap.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first aspect of the invention, the light flux from the light source can be supplied to the near-field light head by a simple constitution and accordingly, the low cost formation can be achieved.
Further, according to a third aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical coupling portion comprises a diffraction grating.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first aspect of the invention, the light flux is coupled to the waveguide by using the diffraction grating and accordingly, in comparison with the case of using the prism, the mass at a surrounding of the near-field optical head can be lightened, tracking at higher speed can be carried out and data reproduction at higher speed can be carried out. Furthermore, the optical coupling portion can be fabricated only by a process similar to the process of fabricating the near-field light head and accordingly, mass production can be carried out and low cost formation can be achieved.
Further, according to a fourth aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical coupling portion comprises optical waveguides laminated to overlap by two stages or more.
Therefore, in addition to the above-described effect, adjustment is facilitated by reducing a number of parts, adjusting portions are reduced and lower cost formation can be achieved. Further, the mass of the near-field light head can be lightened and accordingly, tracking at faster speed can be carried out and data production at higher speed can be carried out.
Further, according to a fifth aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical coupling portion and the optical connecting portion comprise at least one optical waveguide.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first aspect of the invention, it is not necessary to fabricate a clad portion of the optical waveguide fabricated in the near-field light head and accordingly, the fabrication process can be simplified. Further, the number of parts can be reduced and accordingly, in comparison with the case of using the prism or the diffraction grating, optical adjustment is much simplified, adjusting portions are reduced by reducing the number of parts and lower cost formation can be carried out. Further, the mass of the near-field light head can be lightened and therefore, tracking at higher speed can be carried out and data reproduction at higher speed can be carried out.
Further, according to a sixth aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical propagating portion comprises an optical waveguide and a lens for focusing the light flux from the light source to an end face of the optical waveguide.
Therefore, in addition to the above-described effect, the optical propagating portion is constituted by the lens and the optical waveguide for propagating the light flux to the optical connecting portion and accordingly, the optical propagating portion can be fixed to the suspension arm and thin shape formation of the apparatus can be carried out. Further, it is possible to overlap the record media and arrange suspension arms and near-field light heads in correspondence with the respective record media and large capacity formation can be realized.
Further, according to a seventh aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical propagating portion comprises a lens for making the light flux from the light source parallel light flux.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first through the fourth and the sixth aspects of the invention, the optical waveguide of the optical propagating portion can be omitted and accordingly, adjustment is further facilitated by reducing the number of parts and a small-sized and light-weighted information recording and reproducing apparatus can be realized.
Further, according to an eighth aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical connecting portion comprises a mirror for changing an optical path such that light flux from the optical propagating portion is made incident on the optical coupling portion.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first through the fourth, the sixth and the seventh aspects of the invention, in order to couple the light flux from the optical propagating portion to the optical coupling portion, the light flux is bent by the mirror and aerial propagation can be used for the light flux to the near-field light head and accordingly, the flexure structure can effectively be operated and the near-field light head can continue floating up stably. Furthermore, at the location of the aerial propagation, there is constituted a space in which nothing is present and accordingly, mass of the light propagating portion can be lightened and a further light-weighted information recording and reproducing apparatus can be realized.
Further, according to a ninth aspect of the invention, there is provided the information recording and reproducing apparatus wherein the optical connecting portion comprises a diffraction grating for changing an optical path such that light flux from the light propagating portion is made incident on the optical coupling portion.
Therefore, in addition to the effect of the information recording and reproducing apparatus according to the first through the fourth and the sixth through the eighth aspects of the invention, the diffraction grating can freely be designed and accordingly, the light flux having an optimum light distribution can be made incident on the optical coupling portion and accordingly, optical energy can be utilized further effectively.